Carburetor



Sept. 8, 1931. v

P. E. HEFTLER- GARBURETOR Filed Jan. 14, 1930 INVENTOR Patented Sept. 8, 1931 UNI ED STATES PATENT OFFICE PAUL-EMILE HEFTLER, OF DETROIT, MICHIGAN, ASSIGNOR 'IO SOGIETE GENERALE DES GABBUBATEUR ZENITH, OF GENEVA, SWITZERLAND, A CORPORATION OF SWITZER- LAND caniaumrron Application filed January 14, 1930, Serial No. 420,730.

The present invention relates broadly to the art of carburetion, and more particularly to carburetors of the type ordinarily utilized for furnishing the com ustible mixture to internal combustion engines. Even more specifically, the invention relates to that type'of carburetors ordinarily'referred to in the art as plain tube carburetors.

It has long been recognized in-the making 1 of plain tube carburetors that it was desirable to obtain high suction effective on the fuel system without creating too much resistance to the free flow of air to the motor. It has likewise been known that a venturi is capable of givin this suction efl'eet without materially lmpe ing the air flow. Theactual resistance to flow set up by a venturi is proportionate to theeflicienoyof the venturi, and this efiiciency, as a general proposition, depends on the ratio of the length of the venturi to its diameter. As a general rule it may be stated that the longer the venturi, within set limits, the more eflicient it is. In view, however, of the necessity of maintaining the over-all dimensions of a carburetor as small as possible, room has not heretofore been available within the carburetor for the reception of a venturi of such length as to give maximum efliciency.

In accordance with the present invention,

only a small portion of the air supplied to the motor is sub ected to any speeding up action.

Since the delivery of fuel from the fuel systern is directly proportional to the suction effective thereon, it is immaterial, as far as fuel flow is concerned, whether the discharge ocours in a small. or a large tube. By using only a part of the air to create suction on the jet, it is "possible to use a venturi of much smaller diameter and therefore of much,

greater efiiciency, because, for the samelength of carburetor the aspect ratio of the venturi,

i. e., ratio of length to diameter, will bemore conducive to efficiency. is y H o In accordance with the present invention,

" I provide an air system which, as to the ma] or portion of the air flowing therethrough, is not esigned with any regard to suction producing effect, but purely with regard to the capacity of the carburetor. Its characteristics therefore are to produce a maximum flow w1th a minimum of resistance and eddy currents. Cooperating with this is an efiicient single venturi which alone is effective on the fuel system.

In the drawings there is illustrated a carburetor comprising a conventional float chamber 2 having the usual vent opening 3 and provided with the usual inlet 4 for the fuel,

the level of the fuel being automatically controlledbfy a float 5 and needle valve 6. This float chamber is conveniently formed 1n a body casting 7 which casting also provides the usual air intake 8 adapted to be controlled by a choke valve 9.

The air intake 8 communicates with a mixing chamber 10, the outlet from which is controlled by 'a throttle valve 11 operated in any desired manner. Beyond the throttle valve the mixing chamber is continued to pro-.

vide an outlet 12 leading to the engine or engine manifold.

The air intake as to give a maximum'capacity to the carburetor and produce a minimum of eddy cur- .rents. This portion is shaped entirely from this standpoint, and without any regard to any suction producing properties. This portion constitutes ineifect a controlling nozzle or air nozzle whose only function is to conduct air from the air intake to the mixing chamber 10.

Extending coaxially of the portionv 13, is a venturi 14 adapted to select a small portion of the air and submit it to the action of the venturi. This venturi 14 is characterized by having an extremely short. and preferably well rounded mouthpiece 15 and a discharge portion 16 which is relatively long and has a .relativel small angle of divergence. As illustrate in the drawings, it

as a length has a portion 13 so shaped materially greater than the length of the adjusting nozzle, and extends from a point well below the inlet end thereof to a point above the discharge end thereof. By making the venturi of a length such as herein illustrated,

'it is possible to materially improve the effilong discharge cone, thereby insuring an efficient aspect ratio. This suction is transmitted to the fuel system which is herein illustrated as comprising a main suction nozzle 18 and a compensating nozzle '19. The suction nozzle, may be of any well known construction, receiving its fuel directly from the float chamber through a suitable fuel passage 20.

The compensating nozzle, on the. other hand, receives its fuel from a well 21 open at the upper portion to the atmosphere, and communicating with the float chamber through a calibrated orifice 22. A fuel system of this type is well understood in the art,

having been disclosed in the patent to Frans cois The atmospheric well may also have com- Baverey, No. 907,953, of December 29,

municating therewith a suitable idling quill 23 discharging to the mixing chamber through a port 24 conveniently located adjacent the throttle 11.

With a construction of the character herein shown, the suction effective on the nozzles for producing a fuel, dischargetherefrom is that occasioned entirely by the inner venturi. This venturi, however, by reason of its length and design is extremely efficient and therefore produces a suction on the fuel system which is sufficiently great to bring the fuel to the nozzles end, and obtain a fuel discharge of the desired amount for relatively small air flows. This fuel discharging into the venturi mixes with the air flowing therethrough in a region in which the air is travelling at an extremely high velocity. This therefore necessarily produces extremely fine atomization and effectively intermingles the fuel and air.

This mixture having been formed within the venturi, it is preferably maintained out of contact with the air flowing through the air nozzle until such air has been completely passed through such nozzle.

By discharging at a point beyond the point of discharge of the air controlling nozzle, I avoid any interference with the efficiency of flow therethrough and the production of eddies such as necessarily exist where it is attemptedto discharge an appreciable volume of a mixture of different specific gravity into the air which is flowing therethrough. I am thus able to preserve the full efficiency of the air nozzle and to obtain such a high efiiciency with the elongated venturi as to obtain very desirable fuel flow characteristics.

The construction herein illustrated also possesses advantages in that the air nozzle can be so located as not to substantially project into or interfere with the air intake so as to restrict or interfere with the free passage of air therethrough. The venturi, on the other hand, may extend below the lower end of the air nozzle to such an extent as to cooperate with the fuel system the location of which has been previously advantageously determined.

The construction herein illustrated therefore results in a carburetor of maximum capacity in that the flow through the air nozzle is not interfered with, while the flow through the venturi is made much more efficient than that which it has heretofore been considered possible to obtain in a carburetor. Thus, insofar as the fuel system is concerned, it responds only to the suction of a single venturi, this being the suction produced by a venturi of extremely efiicient design. Furthermore, only a comparatively small portion of the total air flow passes through the inner venturi, the maximum flow occurring, as in ordinary single venturi carburetors, through the air nozzle.

In addition to the advantages inherent from the standpoint of capacity, the present construction is highly desirable for the reason that it gives considerable latitude to the designer with respect to the arrangement of the air intake and the location of the fuel system.

While I have herein illustrated and described a preferred embodiment of the present invention, it will be understood that changes in the construction and arrangement of the parts may be made without departing either from the spirit of the invention or the scope of my broader claims, it being appar ent that the invention does not limit itself to use with any particular fuel system or to use with any limited or special venturi contour or design other than the necessary limitations imposed by the claims.

I claim:

1. In a carburetor, an air system characterized by an air nozzle, a venturi within said nozzle and discharging beyond the outlet of said nozzle, and a common mixture chamber for the discharge from both the nozzle and the venturi in which the discharge from the air nozzle is immediately mixed with the discharge from the venturi.

2. In a carburetor, an air system characterized .by a relatively short air nozzle, a relatively longer inner venturi concentric within the air nozzle and projecting beyond the end thereof, and a common mixture chamber for the discharge from to -L the nozzle and the venturi in which the discharge -from the air nozzle is immediatel mixed with the discharge from the venturl.

3. In a carburetor, an air system characterized b an air nozzle, a venturi within said nozz e and discharging beyond the outlet of said nozzle, :1 commonmixture chamber for the discharge from both the nozzle and the venturi in which'the discharge from the air nozzle is immediately mixed with the discharge from the venturi, and a lurality of fuel nozzles discharging into the lower end of the'venturi.

In testimony whereof I have hereunto set my hand.

PAUL-EMILE HEFTLER. 

